Cuffed medical tubes

ABSTRACT

A cuffed silicone tracheostomy tube has two tapered recesses on its outer surface in which opposite ends of a resilient cuff are bonded using an adhesive or solvent. Two shallow ribs extend around the tube on the inner edge of each recess, projecting outwardly to prevent the adhesive or solvent spreading onto the inflatable portion of the cuff. The cuff has several shallow ribs extending around the cuff and spaced along its inflatable portion to promote even inflation.

This invention relates to cuffed medical tubes of the kind having atubular shaft and an inflatable sealing cuff extending coaxially along apart of the shaft, the opposite ends of the cuff being attached with theshaft by an adhesive or solvent in respective annular attachment regionsof the shaft.

The invention is more particularly, but not exclusively, concerned withcuffed tracheal tubes.

It is common practice for tracheal tubes to have an inflatable sealingcuff towards their patient, distal end. The cuff is deflated so that itlies close to the wall of the tube during insertion and is then inflatedvia an inflation line so that the cuff expands and contacts the wall ofthe trachea to provide a seal with patient tissue. In this way, passageof gas along the trachea is confined to flow along the bore of the tube.

The cuffs are of tubular shape extending coaxially along the tube andare attached at opposite ends, or collars, to the outside wall of thetracheal tube shaft. The attachment is typically achieved by means of asolvent or adhesive applied between the collar and the wall of theshaft, or by thermal bonding. These methods of attachment work well withtubes made of PVC and some other plastics but there can be difficultieswith cuffs made of silicone or other highly elastic material where theseare arranged to be a tight fit on the shaft when deflated. In such cuffsthere is a tendency for the cuff-bonding adhesive to seep from the cuffregion towards the region that is intended to be inflatable. This canlead to a poorly-defined attachment border and an irregular shape wheninflated. Also, the longer cure time of some adhesives may make it moredifficult to form a good join.

It is an object of the present invention to provide an alternativecuffed medical tube and a method of manufacture of a cuffed medicaltube.

According to one aspect of the present invention there is provided acuffed medical tube of the above-specified kind, characterised in thateach attachment region has a raised annular rib projecting above thesurface of the shaft at inner ends of the respective regions to restrictflow of adhesive or solvent beyond the attachment regions and onto theinflatable portion of the cuff.

The attachment region towards the patient end preferably includes arecess in which an end of the cuff is attached and preferably, bothattachment regions include a recess in which a respective end of thecuff is attached. The or each recess preferably slopes to provide afrusto-conical surface that is deeper towards the or each end of thecuff Preferably, both recesses slope to provide frusto-conical surfaces,the recesses inclining in opposite senses. The depth of the or eachrecess at one end is preferably substantially the same as the thicknessof the cuff such that there is a substantially stepless transitionbetween the surface of the shaft and the surface of the cuff. The cuffis preferably of a resilient material and is arranged so that itsinflatable portion closely embraces the shaft when deflated. The shaftand cuff are preferably of a silicone material. The cuff may have aplurality of shallow annular ribs on its inner surface spaced from oneanother along the inflatable portion.

According to another aspect of the present invention there is provided amethod of manufacture of a cuffed medical tube including the steps ofproviding a tubular shaft having two annular attachment regions spacedfrom one another along the shaft and bounded by respective annular ribsprojecting above the surface of the shaft at the ends of the regionscloser to one another, providing an inflatable sealing cuff that is aclose fit on the shaft at least at opposite ends of the cuff, applyingan adhesive or solvent to the attachment regions, and applying the cuffto the shaft such that opposite ends of the cuff locate on theattachment regions and are bonded thereto by the adhesive or solvent toleave an inflatable region of the cuff between the bonded ends.

According to a further aspect of the present invention there is provideda cuffed medical tube having a tubular shaft and an inflatable sealingcuff extending coaxially along a part of the shaft and attached with theshaft at opposite ends, the cuff being of a resilient material andclosely embracing the shaft along its entire length when deflated,characterised in that the cuff has a plurality of annular ribs spacedfrom one another along the length of the cuff on the inner surface ofits inflatable portion and adapted to promote even inflation of thecuff.

A tracheostomy tube and its method of manufacture will now be described,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a perspective view of the tube with the cuff inflated;

FIG. 2 is a perspective view of the tube with the cuff removed; and

FIG. 3 is an enlarged cross-sectional view of the patient end of thetube with the cuff omitted.

The tube comprises a curved tubular shaft 1 with a flange 2, close tothe machine end 3, by which the tube is retained in position in atracheostomy. A cylindrical coupling 4 is attached with the shaft 1 andprojects from the machine side of the flange 2. Close to its opposite,patient end 5, a tubular sealing cuff 6 is attached at opposite endcollars 7 and 8 with the outer surface of the shaft 1. The cuff 6, shaft1 and flange 2 are all moulded of a relatively soft silicone material.In its natural, deflated state the cuff 6 is substantially cylindrical,lying close to the surface of the shaft 1. The cuff 6 has severalshallow, internal annular ribs 9 spaced from one another along itscentral inflatable portion 10, the purpose of which will be explainedlater. A small bore inflation line 11 extends along the tube bonded intoa moulded channel 12 along the shaft 1. The inflation line 11 extendsalong one side of the shaft 1, that is, displaced by 90° from the planeof curvature of the shaft. The inflation line 11 extends beneath themachine end collar 7 of the cuff 6; its machine end 13 is terminatedbeneath the inflatable portion 10, being retained between two shallowwedge-shape projections 14 (FIG. 2). These projections 14 act as ananti-occlusion feature to prevent the cuff 6 valving closed the end 13of the inflation line 11 and also protect the cuff from damage by theend of the inflation line.

The two collars 7 and 8 of the cuff 6 are secured with the outer surfaceof the shaft 1 in respective attachment regions 17 and 18 (FIGS. 2 and3). These regions 17 and 18 are provided by shallow annular recess 19and 20 in the surface of the shaft 1. The recesses 19 and 20 each slopeto form frusto-conical surfaces, being deeper at their outer ends andbeing level with the shaft surface at their inner ends, as shown mostclearly in FIG. 3. In this way, it can be seen that the ends of thecollars 7 and 8 on the cuff 6 locate at the deeper end of the recesses19 and 20 respectively. The depth of the recesses 19 and 20 at theirdeeper ends is about 0.38 mm, which is substantially the same as thethickness of the cuff material allowing for a thickness of adhesive usedto bond the cuff collars 7 and 8 to the shaft 1. In this way, there is astepless transition between the surface of the shaft 1 and the surfaceof the cuff 6 at both ends.

The shaft 1 has a further surface feature in the form of two shallowannular ribs 22 and 23 located at the inner end of each recess 19 and20, that is, at the ends of the recesses closer to one another. The ribs22 and 23 project by about 0.2 mm above the surface of the shaft 1 andserve as dams to restrict flow of adhesive or solvent out of therecesses 19 and 20 and inwardly of the cuff 6.

The tube is manufactured by moulding the shaft 1 and flange 2 fromsilicone as a single piece about the coupling 4, which is of a hardermaterial. An adhesive is applied to the inflation line channel 12 andthe inflation line 11 is threaded through a hole 26 in the flange 2 andthen laid into the channel so that its patient end 13 locates betweenthe two wedge-shape projections 14. Adhesive is then applied around thetwo recesses 19 and 20 and the cuff 6 is loaded onto the shaft 1 so thatits end collars 7 and 8 locate in the recesses. It will be appreciatedthat the adhesive or solvent could be applied to the inner surface ofthe collars 7 and 8 instead of directly to the recesses 19 and 20. Theshape and resilient nature of the cuff 6 are such that the cuff closelyand tightly embraces the surface of the shaft 1 along its entire lengthwhen deflated. Without the ribs 22 and 23 there would be a tendency foradhesive in the recesses 19 and 20 to wick between the inside surface ofthe cuff 6 and the shaft surface and flow outside the recesses. Thiswould lead to an uneven boundary of the bonded regions, which in turnwould lead to a distorted shape of the inflatable portion 10 wheninflated. The problem is made worse because of the relatively long curetimes of adhesives used with silicone, which makes it more difficult toattach one collar at a time to the shaft. The frusto-conical shape tothe recesses 19 and 20, however, ensures that there is a smooth,stepless transition between the outside surface of the shaft 1 and thecuff 6 where they meet and also ensures that the cuff can lie inintimate contact with the surface of the recesses along a greater partof their length than would be the case with a recess of cylindricalshape. The taper in the recesses 19 and 20 also helps make the externalsurface of the tube smoother in the region of the ribs 22 and 23. Thesmooth surface presented in the transition regions at opposite ends ofthe cuff 6 facilitates atraumatic insertion and removal through atracheostomy opening. This is more important at the patient end of thecuff 6, for insertion, than at the machine end of the cuff, so it wouldbe possible to use a conventional join at the machine end if desiredalthough preferably, both ends are attached in the same manner.

To inflate the cuff 6, air is supplied via the inflation line 11, suchas by a syringe (not shown) so that it flows out at its machine end 13into the potential space between the cuff 6 and the outside of the shaft1. The ribs 9 around the inside of the cuff 6 channel the air to flowinitially around the tube in an annular channel defined between adjacentribs on either side of the machine end 13 of the inflation line 11. Aspressure increases, these ribs 9 lift away from the surface of the shaft1 to allow air to flow into the adjacent channels and so on. Thisensures that the cuff 6 inflates symmetrically.

The invention could be used with other cuffed medical tubes and is notconfined to tracheal tubes. The tubes could be reinforced with a helicalreinforcement member, such as a wire. Although the invention hasparticular advantages with silicone tubes, it could be used with tubesof various different plastics. The ribs on the inside of the cuff may beused without the ribs on the shaft or the ribs on the shaft may be usedwithout the ribs on the cuff.

1-10. (canceled)
 11. A cuffed medical tube having a tubular shaft and aninflatable sealing cuff extending coaxially along a part of the shaftand attached with the shaft at opposite ends, the cuff being of aresilient material and closely embracing the shaft along its entirelength when deflated, characterized in that the cuff has a plurality ofannular ribs spaced from one another along the length of the cuff on theinner surface of its inflatable portion and adapted to promote eveninflation of the cuff.
 12. The medical tube of claim 11, furthercomprising: respective annular attachment regions to which respectiveends of the cuff is attached by an adhesive or solvent, and a raisedannular rib projecting above the surface of the shaft at each annularattachment region to restrict flow of adhesive or solvent beyond theattachment regions onto the inflatable portion of the cuff.
 13. Themedical tube of claim 12, further comprising: an annular recesses formedabout each of the attachment regions so that there are one and otherrecesses, wherein the annular rib in each attachment region is at theend of the one recess closer to the other recess.
 14. The medical tubeof claim 12, wherein the cuff has a smooth outer surface.
 15. Themedical tube of claim 12, wherein the outer surface of the cuff does nothave the annular ribs.
 16. A cuffed medical tube comprising: a tubularshaft having a patient end and respective annular attachment regionsclose to the patient end, the shaft having a constant outer diameterexcept at the attachment regions; an inflatable sealing cuff extendingcoaxially along the shaft close to the patient end, the opposite ends ofthe cuff being attached with the shaft by an adhesive or solvent in therespective annular attachment regions of the shaft, an inflation lineextending along the outside of the shaft having one end terminatingbeneath the attachment region further away from the patient end into thecuff; wherein each attachment region has a raised annular rib projectingabove the surface of the shaft to restrict flow of adhesive or solventbeyond the attachment regions and onto the inflatable portion of thecuff.
 17. The medical tube of claim 16, wherein the inflation line isbonded into a channel that extends along the outside of the shaft. 18.The medical tube of claim 17, wherein the channel is moulded along theside of the shaft.
 19. The medical tube of claim 16, further comprisingan annular recesses formed about each of the attachment regions so thatthere are one and other recesses, wherein the annular rib in eachattachment region is at the end of the one recess closer to the otherrecess.
 20. The medical tube of claim 16, further comprisingcorresponding annular recesses formed about the attachment regions, theadhesive or solvent being applied to the annular recesses to attach theend collars of the cuff to the shaft.
 21. The medical tube of claim 16,further comprising corresponding annular recesses formed about theattachment regions, the recesses each slope to form a frusto-conicalsurface with the recesses being deeper at their outer ends and beinglevel with the shaft surface at their inner ends.
 22. The medical tubeof claim 16, wherein the shaft and cuff are made of a soft siliconematerial.
 23. The medical tube of claim 16, wherein the cuff has aplurality of annular ribs spaced from one another along the length ofthe cuff on the inner surface of its inflatable portion.
 24. The medicaltube of claim 16, wherein the cuff has a smooth outer surface.
 25. Themedical tube of claim 16, wherein the outer surface of the cuff does nothave the annular ribs.
 26. The medical tube of claim 16, wherein thetube is a tracheostomy tube with the shaft being curved and a flangeclose to a machine end.